Let's break this down. We're going to add 8211 and 1217 together.

Step 1: We'll start by adding the digits 1 & 7 in column 1 and get 8.

Step 2: We'll start by adding the digits 1 & 1 in column 2 and get 2.

Step 3: We'll start by adding the digits 2 & 2 in column 3 and get 4.

Step 4: We'll start by adding the digits 8 & 1 in column 4 and get 9.

So, 8211 + 1217 = 9428.

